I seem to remember being told the average for a first timer is 41+1, and that includes those ergo are induced by 42 (so the 'natural average' may be higher. my first was born at term+16 though a sweep me contracting at term+13 (I declined earlier sweeps).

I hear acupuncture works well, though if I were you, I'd wait until 40w. I know how you feel though. I'm 37w with spd, too. the longer this takes, the more nervous I get, too.